In the conventional active-matrix organic light-emitting diode (AMOLED) display apparatus, a pixel-driving circuit includes a driving transistor for controlling a driving current through each organic light-emitting diode (OLED). The driving transistor is a thin-film transistor (TFT). Due to instability in fabrication process, drift of device parameters, and aging effect of TFT, the driving current varies from one transistor to another and drifts over time to lead to non-uniformity issue in OLED light emission across a display panel of the AMOLED display apparatus. In order to solve the problem of OLED light emission non-uniformity, an approach of external electrical compensation may be adopted to compensate the voltage signal or current signal for operating the OLED.
During the external electrical compensation, a conversion of an analog current signal collected by a signal-collection line to a digital signal is needed. But conventional approach lacks accuracy in the analog-to-digital signal conversion, which affects the effect of the electrical compensation.